LYMPHOID TISSUE

1. Primary – Thymus - Bone marrow

2. Secondary - lymph nodes, lymphoid follicles in tonsils, Peyer's patches, spleen, adenoids, skin, etc. 3. Tertiary - Distributed groups of lymphocytes

Generate lymphocytes fromImmature progenitor cells

Secondary or peripheral lymphoid organs maintain mature naive lymphocytes and initiate an adaptive immune response

Theses are the sites of lymphocyte activation by antigen

Activation leads to clonal expansion and affinity maturation

Mature Lymphocytes recirculate between the blood and the peripheral lymphoid organs until they encounter their specific antigen

GALT Gut associated lymphoid tissue

MALT mucosa-associated lymphatic tissue; lymphoid tissue associated with the mucosa of the female reproductive tract, respiratory tract, etc

SALT Skin associated - dermis of the skin

Precursor cells in the bone marrow produce lymphocytes.

B-lymphocytes (B-cells) mature in the bone marrow. T-lymphocytes (T-cells) mature in the thymus gland.

The  ducts of the lymphatic system provide transportation for proteins, fats, and other substances in a medium called lymph.

Lymph "Means clear water and it is basically the fluid and protein that has been squeezed out of the blood (i.e. blood plasma).

"Unlike the cardiovascular system, the lymphatic system is not closed and has no central pump." 

"Lymph movement occurs despite low pressure due to peristalsis – smooth muscle and skeletal activity (everyday activity and motion of the body).

Nasopharynx

Oropharynx

Laryngopharynx

Oesophagus

Cricoid

Fold by Levator palatini

Salpingopharyngeal fold

Tensor veli palatini Levator veli palatini

The palatine tonsil is an ovoid mass of lymphoid tissue located in the oropharynx between the anterior and posterior pillars

It has a 2 surfaces – medial and lateral and 2 poles – upper and lower

Medial surface

It is lined by stratified squamous non keratinising epithelium which dips into the crypts

The crypts are 12-15 in number

Secondary crypts arise from the primary crypts and extend into the substance of the tonsil

On of the crypts located in the upper part are larger than the rest – crypta magna

It represents the ventral part of second pharyngeal pouch

The crypts serve to increase the surface area of the tonsil

The crypts may be filled witth cheesy material – epithelial debris, food particles and bacteria

Lateral surface

It is covered by the fibrous capsule of the tonsil The tonsillar bed is separated from the capsule by loose areolar tissue

This makes it is easy to dissect the tonsil from its bed during tonsillectomy

It is the site of collection of pus in peritonsillar abscess (quinsy)

Some fibers of palatoglossus and palatopharyngeus gets attached to capsule of tonsil

Bed of tonsil

It is formed by the 2 muscles

Superior constrictor

Styloglossus

Tensor veli palitini Lavator veli palitini

Palatopharyngeus

Structures related to bed of tonsil

The tonsil is separated from its bed by loose areolar tissue. The structures forming the bed of the tonsil are:Superior constrictor muscleStyloglossus muscle

The structures related to the bed of the tonsil are:

styloid process (if enlarged)

glossopharyngeal nerve

facial artery

submandibular salivary gland

posterior belly of digastric

medial pterygoid muscle

angle of mandible

PS: Palatine / External palatine / Paratonsillar vein

Upper pole

It extends into the soft palate

There is a semilunar fold of mucous membrane which covers the medial part of the upper pole

It extends from anterior pillar to posterior pillar

It encloses a potential space – supratonsillar fossa

Lower pole

It is attached to the tongue A triangular fold of mucous membrane extends from the anterior tonsillar pillar to the lower pole

It encloses a space – anterior tonsillar space

The lower pole is separated from the tongue by the tonsillo-lingual sulcus

This sulcus may harbour carcinoma

Blood supply

The tonsil is supplied by branches of external carotid artery

The tonsil is supplied by 5 arteries:

Tonsillar branch of facial artery (main supply)

Ascending palatine branch of facial artery

Ascending pharyngeal branch of external carotid artery

Dorsal linguae branch of lingual artery

Descending palatine branch of maxillary artery

Blood supply from medial surface

Venous drainage

Blood from the tonsil drains into the paratonsillar vein which in turn drains into the common facial vein and pharyngeal venous plexus

Lymphatic drainage

Lymphatics from the tonsil pierce the superior constrictor and drain into the upper cervical lymph nodes especially jugulodigastric (tonsillar)lymph node

Enlarged non tender jugulodigastric lymph node is a sign of chronic tonsillitis

Facial vein

Omohyoid muscle Supraclavicular nodes

Digastric muscle

Internal Jugular vein

Jugulo-omohyoid node

JUGULO-DIGASTRIC NODE

Nerve supply

Lesser palatine branch of sphenopalatine ganglion Glossopharyngeal nerve

Nerve supply

Lesser palatine branch of sphenopalatine ganglion Glossopharyngeal nerve

Waldeyer’s lymaphatic ring

Functions of tonsil

It has a protective function in that it prevents entry of pathogens through the nasal and oral route

The crypts on the surface of the tonsil serve to increase the surface area and increase the efficiency of protection against pathogens It forms a part of Waldeyer’s lymphatic ring

Applied anatomy

Tonsils prevent infection. Infected tonsils act as septic focusDamage of paratonsillar vein during tonsillectomy leads to excessive venous haemorhhageDamage to glossopharygeal nerve leads to loss of taste sensationInfected tonsillar pain may be referred to middle ear because ofSame nerve supply